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Re: gpsd hardware with RTK support?

From: Gary E. Miller
Subject: Re: gpsd hardware with RTK support?
Date: Mon, 21 Nov 2022 16:34:32 -0800

Yo Greg!

On Mon, 21 Nov 2022 19:28:21 -0500
Greg Troxel <> wrote:

> "Gary E. Miller" <> writes:
> >> MaCORS can send on various mountpoints (for carrier phase, omitting
> >> CMR):
> >> 
> >>   RTCM 3.x (Extended) : GPS/GLO only
> >>   RTCM 3.x (MSM4)     : GPS/GLO/GAL/BDS including GPS L5  
> >
> > Only MSM4?  Sad.  
> I have not found info that really makes the case that MSM7 is better
> in practice.

To quote the standard that I obviously do not have a pirate copy of:

    "Messages MSM1 – MSM5 are standard precision messages and messages
    MSM6 and MSM7 are high precision messages. "

> >>  I am using MaCORS which is
> >> Leica and I go into FIX very easily (given good sky view) and have
> >> observed 4 cm repeatability when occupying the same mark days
> >> later.  
> >
> > 4cm not that great these days.  
> For F9P, $100-class antenna and RTK where the reference receivers are
> in the 25 km range, vs 500m, I think it is.  People quote theoretical
> accuracies all the time, and I'm talking about actually making repeat
> measurements on a real mark with some tree cover.  At this degree of
> accuracy you need to be careful about leveling; I was hand-holding a
> prism pole with a bubble level.

Good for your application, but not as good as it can get.

> I would be very interested to see similar data from others, doing:
>   establish some point that you can return to
>   measure it with RTK (and a prism pole or tripod) once, with a 30s
>   average, and compute the mean with qgis etc.
>   several days later, do it again, wait a few more days, do it a third
>   time
>   talk about the extreme spread of the 3 measurements, longest side of
>   the triangle.  Explain the RTK reference source, leveling method,
> and antenna.

Maybe after the next release.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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